Last month, Firefox accounted for 38.1% of the market share in Europe, compared to 37.5% for Internet Explorer. Google's (GOOG) Chrome had a 15% share.

But Firefox has Chrome to thank, at least partly, for its ability to overthrow Internet Explorer as the European browser leader. Google's browser has quickly been gaining popularity overseas -- nearly tripling its European usage in the past year, according to StatCounter -- and stealing market share from Microsoft.

Still, Internet Explorer has maintained a strong lead in North America, where it makes up 49% of the market, compared to Firefox's 27%, Chrome's 13% and Safari's 10%, StatCounter says.